1/*
2 * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
3 * Copyright (C) 2009 Google Inc. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
15 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
17 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
18 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
19 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
20 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
21 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
22 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include "config.h"
28#include "platform/ThreadTimers.h"
29
30#include "platform/PlatformThreadData.h"
31#include "platform/SharedTimer.h"
32#include "platform/Timer.h"
33#include "platform/TraceEvent.h"
34#include "platform/scheduler/Scheduler.h"
35#include "wtf/CurrentTime.h"
36#include "wtf/MainThread.h"
37
38namespace blink {
39
40// Fire timers for this length of time, and then quit to let the run loop process user input events.
41// 100ms is about a perceptable delay in UI, so use a half of that as a threshold.
42// This is to prevent UI freeze when there are too many timers or machine performance is low.
43static const double maxDurationOfFiringTimers = 0.050;
44
45// Timers are created, started and fired on the same thread, and each thread has its own ThreadTimers
46// copy to keep the heap and a set of currently firing timers.
47
48static MainThreadSharedTimer* mainThreadSharedTimer()
49{
50    static MainThreadSharedTimer* timer = new MainThreadSharedTimer;
51    return timer;
52}
53
54ThreadTimers::ThreadTimers()
55    : m_sharedTimer(0)
56    , m_firingTimers(false)
57    , m_pendingSharedTimerFireTime(0)
58{
59    if (isMainThread())
60        setSharedTimer(mainThreadSharedTimer());
61}
62
63// A worker thread may initialize SharedTimer after some timers are created.
64// Also, SharedTimer can be replaced with 0 before all timers are destroyed.
65void ThreadTimers::setSharedTimer(SharedTimer* sharedTimer)
66{
67    if (m_sharedTimer) {
68        m_sharedTimer->setFiredFunction(0);
69        m_sharedTimer->stop();
70        m_pendingSharedTimerFireTime = 0;
71    }
72
73    m_sharedTimer = sharedTimer;
74
75    if (sharedTimer) {
76        m_sharedTimer->setFiredFunction(ThreadTimers::sharedTimerFired);
77        updateSharedTimer();
78    }
79}
80
81void ThreadTimers::updateSharedTimer()
82{
83    if (!m_sharedTimer)
84        return;
85
86    if (m_firingTimers || m_timerHeap.isEmpty()) {
87        m_pendingSharedTimerFireTime = 0;
88        m_sharedTimer->stop();
89    } else {
90        double nextFireTime = m_timerHeap.first()->m_nextFireTime;
91        double currentMonotonicTime = monotonicallyIncreasingTime();
92        if (m_pendingSharedTimerFireTime) {
93            // No need to restart the timer if both the pending fire time and the new fire time are in the past.
94            if (m_pendingSharedTimerFireTime <= currentMonotonicTime && nextFireTime <= currentMonotonicTime)
95                return;
96        }
97        m_pendingSharedTimerFireTime = nextFireTime;
98        m_sharedTimer->setFireInterval(std::max(nextFireTime - currentMonotonicTime, 0.0));
99    }
100}
101
102void ThreadTimers::sharedTimerFired()
103{
104    TRACE_EVENT_SET_SAMPLING_STATE("blink", "BlinkInternal");
105
106    // Redirect to non-static method.
107    PlatformThreadData::current().threadTimers().sharedTimerFiredInternal();
108
109    TRACE_EVENT_SET_SAMPLING_STATE("blink", "Sleeping");
110}
111
112void ThreadTimers::sharedTimerFiredInternal()
113{
114    // Do a re-entrancy check.
115    if (m_firingTimers)
116        return;
117    m_firingTimers = true;
118    m_pendingSharedTimerFireTime = 0;
119
120    double fireTime = monotonicallyIncreasingTime();
121    double timeToQuit = fireTime + maxDurationOfFiringTimers;
122
123    while (!m_timerHeap.isEmpty() && m_timerHeap.first()->m_nextFireTime <= fireTime) {
124        TimerBase& timer = *m_timerHeap.first();
125        timer.m_nextFireTime = 0;
126        timer.m_unalignedNextFireTime = 0;
127        timer.heapDeleteMin();
128
129        double interval = timer.repeatInterval();
130        timer.setNextFireTime(interval ? fireTime + interval : 0);
131
132        TRACE_EVENT2("blink", "ThreadTimers::sharedTimerFiredInternal",
133            "src_file", timer.location().fileName(),
134            "src_func", timer.location().functionName());
135
136        // Once the timer has been fired, it may be deleted, so do nothing else with it after this point.
137        timer.fired();
138
139        // Catch the case where the timer asked timers to fire in a nested event loop, or we are over time limit.
140        if (!m_firingTimers || timeToQuit < monotonicallyIncreasingTime() || (isMainThread() && Scheduler::shared()->shouldYieldForHighPriorityWork()))
141            break;
142    }
143
144    m_firingTimers = false;
145
146    updateSharedTimer();
147}
148
149void ThreadTimers::fireTimersInNestedEventLoop()
150{
151    // Reset the reentrancy guard so the timers can fire again.
152    m_firingTimers = false;
153    updateSharedTimer();
154}
155
156} // namespace blink
157
158